The present invention relates to fuel supply systems for internal combustion engines; more particularly, to devices for controlling fuel supply pressure; and most particularly, to a fuel pressure regulator wherein a valve and diaphragm assembly is axially offset from a valve seat orifice to prevent large hysteresis values and audible noise.
Fuel supply systems for internal combustion engines are well known and typically include means for maintaining a predetermined inline pressure of fuel being supplied to fuel injectors or carburetors or the like. A prior art fuel pressure regulator typically includes a valve having a matable seat and head. The valve seat includes a center-aligned fuel orifice. The fuel orifice is aligned with the centerline of the valve head, which causes the resulting opening and closing forces to be aligned on the same centerline, desirably providing a force balance to the regulator and intending to maintain a parallel orientation between the valve head and the seat. The valve head is generally pawn-shaped and includes a ball mounted on a stem and pivotably captured in a fixed retainer. Because the ball may swivel in the retainer, the valve head is undesirably responsive to flow cavitation turbulence occurring in the fuel orifice, resulting in valve vibration and audible noise (valve chatter). Because of this chaotic instability, the valve head sealing surface either can remain parallel to the valve seat sealing surface or can settle on the edge of the seat sealing surface at any one of an infinite number of angular positions. Because of minute pressure fluctuations on the sealing surface of the valve head, caused by cavitation, the valve head tends to flutter among ever-changing rest points on the seat. If the valve head does pivot and hereby remains in contact with the seat as flow rate is decreasing, the pressure at the set point flow rate will be significantly less than the actual increasing flow rate value (flow hysteresis). Audible noise and large hysteresis values can affect user satisfaction and also cause manufacturing problems and high reject rates.
What is needed is a fuel pressure regulator which is silent and lacks flow hysteresis.
It is a principal object of the present invention to provide an improved fuel pressure regulator wherein a valve head has a single and preferred mating position with a valve seat.
It is a further object of the invention to provide such a regulator which is simple and inexpensive to manufacture.
It is a still further object of the invention to reduce the manufacturing cost and waste for fuel pressure regulators.
Briefly described, a fuel pressure regulator in accordance with the invention includes a valve head and diaphragm assembly having a centerline offset from the centerline of a corresponding valve seat and fuel orifice. This may be accomplished either by offsetting the valve head and diaphragm assembly in the pressure regulator with respect to the seat and orifice, by offsetting the orifice in the seat with respect to the head and diaphragm assembly, or by inducing offsetting axes between the valve head and seat orifice.
The pressure differential between the control pressure above the valve and the backpressure on the fuel orifice results in a closing force that acts along the centerline of the fuel orifice. Since the vector of this force does not align with the centerline of the valve head and diaphragm assembly, a torque on the valve head is always present which acts on the valve swivel point to keep the valve in a stable, pivoted position at all flow rates. The valve head always makes contact with the valve seat along the sealing surface edge at the contact point having the shortest distance to the seat orifice centerline. Because the valve head maintains this single point contact during regulator operation, the pressure instability and noise problems are eliminated.